Coordinate table

ABSTRACT

An X-Y coordinate table wherein straight line motion is provided by a frame member which is coupled to the top of said coordinate table via linkages in such a manner that any circular arc motion of the table top is compensated for by an opposite circular arc motion of the frame member.

United States Patent Shaw [451 Aug. 1, 1972 [54] COORDINATE TABLE2,508,281 5/1950 Miller et al. ..74/459 72 Inventor: B i Herbert Shaw,Hove England 3,241,243 3/1966 Speer ..33/l M 3,529,481 9/1970 Budzyn..33/1 M [73] Assigneez International Standard Electric Cor porauon NewYork Primary Examiner-William F. ODea [22] Filed: May 7, 1970 AssistantExaminer-Wesley S. Ratliff, Jr.

Attorney-C. Cornell Remsen, Jr., Walter J. Baum, [211 App]' 35367 PaulW. Hemminger, Charles L. Johnson, Jr., Philip M. Bolton, Isidore Togut,Edward Goldberg and [30] Foreign Application Priority Data Menotti J.Lombardi, Jr.

M l 196 t 4,4

ay 3 9 Grea Britain 2 12/69 ABSTRACT U-S- CL M An X-Y coordinate tablewherein Straight line motion [51] Int. Cl ..F16h 27/02 is provided by aframe member which i coupled to [58] held of Search"74/89'15 459; 33/1174 TA the top of said coordinate table via linkages in such a mannerthat any circular arc motion of the table top is [56] References cuedcompensated for by an opposite circular arc motion of UNITED STATESPATENTS the frame member- 3,495,519 2/ 1970 Alfsen et al. ..33/l M 3Claims, 2 Drawing Figures PATENTEDAuc 1 I972 3,680,401

SHEET 1 BF 2 30+ i 4 x s Inventor BRIAN HERBERT SHAW YMM A tlorneyPATENTEmus "1 m2 3 680,401

SHEET 2 BF 2 Inventor BRIAN HERBERT SHAW A Home} BACKGROUND OF THEINVENTION This invention relates to an X-Y coordinate table and, moreparticularly, to such a table having extreme accuracy of straightlinemotion and freedom from backlash and friction.

X-Y coordinate tables presently known in the art often have thedisadvantage that the table top motion describes a circular arc due tothe mode of linkage connections made. A further disadvantage of priorart systems is that they are relatively inaccurate due to backlash andfriction between the linkages and the member to be moved.

SUMMARY OF THE INVENTION Therefore, the main object of this invention isto provide an X-Y coordinate table which is relatively free frombacklash and friction.

It is a further object of this invention to provide such a coordinatetable which has substantially level straight line movement.

According to the present invention there is provided an X-Y coordinatetable having table member movable in two orthogonal straight linemovements, wherein the apparatus provided for each straight linemovement comprises a rigid frame, a first plurality of links coupling afirst movable member to said rigid frame, a second plurality of linkscoupling said movable table member to said first movable member, and anextension link equal in length to one of said second plurAlity of linkscoupled to one end of said one link, and a third link coupling the otherend of said one link to said rigid frame, said extension link and saidthird link being slave links for constraining the movement of said firstmovable member.

Further objects and features of this invention will become more apparentby, reference to the following description taken in conjunction withaccompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of apreferred embodiment of the invention illustrating the linkages utilizedin X-axis motion; and

FIG. 2 illustrates a perspective view of a coordinate table with X and Yaxis movement.

DESCRIPTION OF THE PREFERRED EMBODIMENT The X-Y movement of thecoordinate table shown in FIG. 2 is constructed from two straight linemovements combined at right angles to each other. One such straight linemovement will now be described with reference to FIG. 1.

Member 1 is a portion of the table which is required to have straightline movement in the directions indicated. It is supported by rigidlinks 2 and 3 and a second movable member 4, which is in turn supportedby rigid links 5 and 6 on a fixed frame 7. The rigid links 5,2, 6, and 3each may have four flexure bearings (e.g.3033 shownin FIG. 2), one ateach corner of the links and forming an approximate square if viewedfrom 8 in FIG. 1.

If the movement of member 1 is to be accurately confined to a straightline, member 4 must be constrained or slaved to move by half the amountof movement of member 1. This constraint is provided by slave links 9and 10. Link 9 is a rigid extension of link 2 and r the lengths of links2 and 9 are equal. Point 11 is fixed relative to the fixed frame 7 inthe horizontal plane, but

is free to move slightly in the vertical plane. Ideally the locus ofpoint 11 should be a vertical straight line, but it can be shown thatwith the very small movements involved, the are due to the link 10introduces errors in the movements of 4 and l which are too small to bedetected even in the highest accuracy systems.

In a preferred embodiment of the coordinate table, member 1 moves atotal of two inches, i.e., 1 inch either side of the position with thelinks 2 and 3 vertical, and 4 is, therefore, constrained to move half aninch either side of this position. Member 1 is driven linearly (back andforth along the direction of the X axis) by a preloaded ball leadscrewand nut arrangement coupled to a drive motor, as shown schematically byshaft 34, and acting on fixed extension 21 of 1, and midway between 1and 4 for maximum stability. The bearings used are preferably flexurepivots and have no separate parts, do not suffer from backlash orfriction, and have great rigidity in all directions other than rotation.

As previously stated, two straight line movements, one such movementbeing shown in FIG. 1, are combined to form the coordinate table. InFIG. 2, if FIG. 1 is taken as representing the outer system (X-axis)some of the parts can be identified by the corresponding numbers. Forthe sake of convenience, the bearings in FIG. 2 are shown as metallicflexure strips. For example, two of link Ss four flexure bearings areindicated at 30 and 31 and two of rigid link 2s four flexure bearingsare indicated at 32 and 33. The motors are represented by 12 and 13 inthe X and Y axis respectively. The Y-axis system is also mounted tomember 1 with the drive system thereof coupled to fixed extension 20 ofmember 1, not unlike the drive system arrangement associated with the Xaxis as above described.

The Y axis system, in fact is identical to the X axis system and as tothe components thereof shown in FIG. 2, 13 corresponds to 12 in the Xaxis, 14 corresponds to 9, 15 corresponds to l0, 16 corresponds to 2, 17corresponds to 4, 18 corresponds to 5, 19 corresponds to 6, and 20 and21 are the extensions respective fixed of l which are operativelycoupled to the drive means 13 and 12 respectively, for Y and X axismovement respectively.

The coordinate table is further provided with means (not shown) foraccurately aligning the two axes at right angles.

It is to be understood that the foregoing description of this inventionis made by way of example only and is not to be considered as alimitation on its scope.

I claim:

1. An X-Y coordinate table having a table member movable in twoorthogonal straight line movements, wherein the apparatus provided foreach straight line movement comprises:

a rigid frame;

a first movable member;

a first plurality of links coupling said first movable member to saidrigid frame;

a second plurality of links coupling said movable table member to saidfirst movable member;

an extension link equal in length to one of said 5 ure bearings.

3. An X-Y coordinate table according to claim 2 further including:

a pair of extensions from said table member, one for X-axis movement andthe other for Y-axis movement; and

a pair of independent driving means, one each for X- axis and Y-axismovement, said driving means acting on the respective extensions at aposition on said extension midway between said table member and saidfirst movable member.

1. An X-Y coordinate table having a table member movable in twoorthogonal straight line movements, wherein the apparatus provided foreach straight line movement comprises: a rigid frame; a first movablemember; a first plurality of links coupling said first movable member tosaid rigid frame; a second plurality of links coupling said movabletable member to said first movable member; an extension link equal inlength to one of said second plurality of links coupled to one end ofsaid one link; and a third link coupling the other end of said one linkto said rigid frame, said extension link and said third link being slavelinks for constraining the movement of said first movable member.
 2. AnX-Y coordinate table, according to claim 1, wherein said links arecoupled to said members by flexure bearings.
 3. An X-Y coordinate tableaccording to claim 2 further including: a pair of extensions from saidtable member, one for X-axis movement and the other for Y-axis movement;and a pair of independent driving means, one each for X-axis and Y-axismovement, said driving means acting on the reSpective extensions at aposition on said extension midway between said table member and saidfirst movable member.